Fixed pros Final

Proper room size and configuration of a dental room

10 ft x 12 ft

proper lighting in a dental setting (light accommodation)

-Room light =250-400 lumens,

-Operating light = 3000 lumens.

-contrast ratio = 10:1

What things are involved in creating a supportive environment in dentistry

- proper equipment

-proper room size and configuration

- proper lighting

elements of a "balanced posture": feet, thighs, elbows, shoulders, back/neck

- Feet flat on the floor (legs should not eb sloping downward. ("Tripoding")

- Thighs parallel with the floor or sloping slightly downward.

- Elbows close to your body.

- Shoulders parallel to the floor.

- Back and neck rather upright.

elements of a "balanced posture": nose to oral cavity distance ...Why?

14" to 18" (Better posture, infection control, acceptable social distance)

elements of a "balanced posture": oral cavity and operative field

- Place oral cavity at or slightly above elbow height.

- Place operative field in your midline. (Depth perception)

Working in an unfavorable configuration can lead to:

Backache

General fatigue

Eye fatigue

Headache

Irritability and impatience

Varicose veins (if standing)

Hip pain (if standing)

Plantar fasciaitis (if standing)

Where should the assistant be (compared to doctor) to establish a balanced posture for the assistant

Height 4"- 8" above dentist (to see past left cheek)

What things help with eye fatigue

-light accommodation

-focal accommodation (reduce look-ups from op field)

- magnified vision

common reasons for not using balanced posture

Poor positioning of the patient.

Blocked vision

Poor lighting

Pre-occupation with the procedure

classification of motion: class I

Movement of the fingers only as when picking up a small item.

T/F the operator should be positioned to the patient

F (position the patient to the doctor)

a circle radius of ______ minimizes movements to: _____ +______

- 25-30

-perform repetitious tasks

-minimize eye fatigue

Classification of Motion CLASS II :

Fingers and wrist motion: transferring an instrument to the operator, or manipulating a hand instrument.

Classification of Motion CLASS III :

Fingers, wrist, and elbow as when reaching for a handpiece.

Classification of Motion CLASS IV :

The entire arm and shoulder: reaching for supplies away from the work area, or to adjust the operating light

Classification of Motion CLASS V :

The entire torso: turning around to reach for equipment from adjacent fixed cabinetry

Which classes of motion should be eliminated

IV, V

What does the metal-ceramic restoration consists of

metal substructure supporting a ceramic veneer that is mechanically and chemically bonded to it

The chemical component of the bond of a metal ceramic restoration is achieved through ______

firing

type of Metal Ceramic Restoration (3)

- Metal ceramic crowns

- Porcelain fused to metal (PFM) crowns

- Ceramic-veneered crowns

indications of a metal ceramic restoration

- Extensive coronal destruction

- maximum retention and resistance form

- correction of axial wall

- restore endodontically treated teeth

T/F all ceramic restorations are more esthetic than metal ceramic ones.

true

contraindications of a metal ceramic restoration

➡ Patients with active caries or untreated periodontal disease

➡ Young patients with large pulp chamber

➡ When more conservative restorations is feasible

Advantages of a metal ceramic restoration

➡ Strength of the complete cast restorations with the esthetics of all ceramic crown

➡ Better choice to serve as a retainer for FPDs (fixed partial denture) because its metal substructure can accommodate cast or soldered connectors.

➡ can be used for survey crowns: modified to incorporate occlusal and cingulum rests and milled proximal and reciprocal guide planes in their metal substructure.

Disadvantages of Metal Ceramic Restoration:

➡ Requires significant tooth reduction

➡ In highly esthetic area, the margin needs to be placed subgingivally which increases the potential for periodontal disease.

➡ slightly inferior esthetic.

➡ Fracture of ceramic layer when it is not designed or processed properly.

➡ Difficult shade selection

➡ More expensive laboratory costs

Metal Alloy Options for Metal Ceramic Restorations

-high noble allows

-titanium and titanium alloys

-nobble alloys

-predominantly base alloys

requirement of high-noble alloy ceramic restoration

-noble metal content > 60% (gold + platinum group metal) and gold > 40%

requirement of titanium and titanium allow ceramic restoration

titanium > 85%

requirement of noble alloy ceramic restoration

noble metal content >25 (gold + platinum group metal)

requirement of predominantly base alloy ceramic restoration

noble metal content < 25 (gold + platinum group metal)

what are the platinum group metals

-platinum

-palladium

-rhodium

-iridium

-osmium

-ruthenium

properties of high noble/noble metal alloys

➡ good corrosion resistance

➡ Au-Pt-Pd alloys have desirable yellow color ➡ Indium (In), Tin (Sn) and Iron (Fe) are added to form oxides to produce desirable ceramic-metal bond

key components of the base metal alloys

-chromium

-molybdenum

-Ti (may become important in the oxide layer)

role of chromium in a base metal alloy

provides tarnish and corrosion resistance

role of molybdenum in a base metal alloy

added to decrease the thermal coefficient of expansion

advantages of base metal alloys

- superior mechanical properties compared to noble or high-noble alloys (elastic moduli and hardness are high).

- may be etched for resin bonding.

negative characteristics of base metal alloys

- higher corrosion in acidic environments;

- difficult finishing and polishing;

- dark, thick oxides;

- risk of patient allergy;

- difficult soldering.

- liquidus temperatures are the highest among all prosthodontic alloys --> harder to cast them and ensure appropriate marginal fit of restorations

main components of porcelain

-quartz (Silica-SiO2)

-feldspar

-other oxides

type of feldspar in porcelain

- potassium aluminum silicate orthoclase

- sodium aluminum silicate

Applications of high fusing porcelain

-denture teeth

-fully sintered alumina and zirconia core ceramics

high fusing porcelain sintering temp range

> 1300 C

medium fusing porcelain sintering temp range

1101-1300 C

low fusing porcelain sintering temp range

850 - 1100 C

ultralow fusing porcelain sintering temp range

< 850 C

Applications of medium fusing porcelain

-denture teeth

-presintered zirconia

Applications of low fusing porcelain

-crown and bridge veneer ceramic

Applications of ultralow fusing porcelain

-crown and bridge veneer ceramic

what is fusion temperature

powder particles of dental ceramic fuse together during firing

When is porcelain strong and when is it weak

Porcelain is strong under compression but weak when placed under tension

what is the coefficient thermal expansion

The change in length per unit length of a material for a 1 degree C change in temperature

coefficient theramal expansion of the metal alloy needs to be slightly ______ than the dental ceramic

higher

factors affecting the bond of a metal ceramic restoration

-oxide layer b/w metal and ceramic

-abrasion with aluminum oxide (alumina) on alloy castings to provide mechanical interlocking.

- thermal expansion must closely match --> strong interfacial bond

fabrication of a metal ceramic restoration

• Opaque layer

• Body porcelain

• Enamel porcelain

• Surface glaze

proper way to wax when creating a metal-ceramic crown

- Wax the crown to the full tooth shape first, then cut it back evenly so the porcelain layer is uniform —> this gives better strength and more consistent color

shape of a metal ceramic preparation

- Avoid sharp angles or pits on the veneering surface because they can contribute to internal stress in the fired porcelain.

➡ Convex surfaces and rounded contours (reduces stress)

➡ Smooth surface facilitates wetting of the framework by the porcelain slurry.

properties of a Metal preparation: metal-ceramic junction

- should be as definite (90-degree angle) and as smooth as possible

properties of a Metal preparation: metal framework minimum thickness

-must be thick enough

-minimum thickness 0.3 mm for noble metal alloys

- minimum thickness 0.2 mm for base metal alloys

properties of a Metal preparation: interface

must be far away (at least 1.5 mm) from all centric occlusal contacts and must be distinct

how is the investment layer of a metal perp removed

-ultrasonic

-airborne particle abrasion

-steam

what is the investment layer/material of a metal prep

the mold material surrounding the casting

how is the oxide layer that has been formed on the metal surface during casting removed

-should be partially removed with acid or air abrasion

why is it important to remove the investment and oxide layer of a metal prep

Achieving a successful bond depends on a controlled thickness of the metal-oxide layer

When finishing the metal surface before applying porcelain, the metal should be ground or polished in ________?

one direction (not back and forth)

why should metal finishing be done in one direction and not back and forth movements?

- Grinding in multiple directions can drag metal particles and debris across the surface, trapping air and contaminants in the metal surface

-trapped debris can cause bubbles, defects, or contamination in the porcelain layer

what should be used to finish/smooth a metal prep

-ceramic-bound stones

-tungsten carbide burs

after the metal prep surface has been smoothed, what should it be abraded with?

-aluminum oxide

less than _____ thickness of a metal substructure may lead to distortion during firing.

.3 mm

what is used to finish the nonveneering surface of the metal substructure

rubber wheel stage

what is used to finish the veneering surface of the metal substructure

ceramic-bound stone

- airborne particle abrasion on veneering area (protect margin with soft wax)

what bur is used to finish the metal-ceramic junction of the metal substructure

tungsten carbide bur

how to clean the metal substructure

➡ Immersion in a general-purpose cleaning solution in an ultrasonic unit for 5 minutes.

➡ Steam cleaning

what is the purpose of the oxide layer on the metal surface

establish the chemical bond between metal and porcelain

how do you create the oxide layer on a metal substructure

Inserting substructure into a porcelain furnace above the porcelain firing temperature with or w/o vacuum.

-- High noble alloy: longer holding time

-- Noble: less holding time

which metal does not require a oxidizing cycle

base metal

purpose of opaque porcelain layer

-bonds to the alloy

-masks the color of the alloy

layers of dental porcelain

1. opaque porcelain

2. dental porcelain powder (body and enamel)

purpose of the body layer of dental porcelain

provides most of the shade to match natural teeth and bonds to the opaque porcelain

enamel layer of dental porcelain

most translucent

condensation technique of dental porcelain

- Vibration and blotting help water move out by capillary action (water pulled out from between particles)

-Gentle patting with a brush and light tapping on the cast produces adequate vibration during the preliminary stage of condensation. A tissue is held close for removal of excess surface moisture.

what is the process used to harden dental porcelain

sintering

what occurs during sintering? what does this create?

- When the mass is heated, individual porcelain particles conglomerate and bridge together.

- a loss of interstitial space occurs, accompanied by as much as a 27% to 45% volumetric shrinkage

how do you get the porcelain teeth to look shiny similar to natural teeth

-a bisque baked ceramic (porcelain is first fired= matte) needs to be glazed

-surface of porcelain is vitrified during glazing (melts turning it into a glassy, smooth coating)

what is glazing

process of making porcelain look smooth and shiny

glazing techniques

-autoglazing

-overglazing

what is autoglazing

Oven temperature is raised to the fusion temperature and the bisque baked is maintained in that temperature before cooling. - occlusal contacts are altered during glazing

what is overglazing

A separate mix of powder and liquid is applied to the surface and the restoration is fired

internal characterization of adding colored pigment

Pigments can be incorporated in the opaque, body, or incisal powder

external characterization of adding colored pigment

- performed during overglazing

- pigments are added to the surface of the bisque baked porcelain then they are fired in glazing temperature

The most common complications associated with conventional single crowns were:

- need for endodontic treatment (3%)

- porcelain fracture (3%)

- loss of retention (2%)

- periodontal disease (0.6%)

- and caries (0.4%).

four primary roles of a metal substructure

(1) provides the fit of the restoration to the prepared tooth,

(2) produces surface oxides that bond to dental porcelain,

(3) serves as a rigid foundation to which the brittle porcelain can be attached for increased strength and support

(4)restores a tooth's proper emergence profile

five secondary functions of a metal substructure

(1)allows articulation on metal occlusal and lingual surfaces,

(2)permits restoration in metal when insufficient clearance is available for porcelain,

(3)makes it easy to adjust and repolish surfaces that have been adjusted intraorally,

(4) supports extracoronal components of a removable partial denture (ie, rest seats, guiding planes),

(5) houses attachments for a fixed or a removable partial denture.

The centric stops (occlusal contact) of any metal-ceramic restoration can be located on either _______ or _______

porcelain

metal

the centric stops (occlusal contact) must be at least _____ away from the metal-ceramic junction.

1.5 mm

Opposing restorations must be carefully planned so that contacting surfaces are of the ______

same material

The thickness of a ceramic veneer must not exceed ______

2 mm

a minimum thickness of _____ is needed for an esthetically pleasing restoration of a ceramic veneer.

1 mm

what are the three designs for the margin of a metal ceramic crown

-metal collar

-metal disappearing ceramic metal

-ceramic margin

metal collar finish line

- rounded shoulder (deep chamfer) finish line

-90-degree (square shoulder) bevel finish line

advantages of a metal collar margin/ when is it useful

-provides excellent adaptation

-useful for non-esthetic area